The week before that, Hudson’s Bay Co.’s Lord & Taylor had a dress sell out quickly after 50 fashion influencers were paid to post photos and tag them #designlab to highlight its new collection.

These two cases support a trend highlighted by think tank L2, which noted that Instagram has the highest browser-to-shopper conversion rate of the social media outlets they track.

Credit Suisse analyst Michael Exstein pointed out that this finding is impressive given that Instagram doesn’t usually allow retailers to post active web links in picture descriptions. However, the app makes it easy for brands to directly engage with customers through things such as photo contests, where followers include specific hashtags with pictures in hopes of winning gift cards or other prizes.

“The rise of Instagram follows efforts at Facebook and others to commercialize social media,” Exstein said in a report.

He highlighted a survey showing that while some retailers are more successful than others in gaining followers and encouraging engagement, social media and Instagram in particular are clearly powerful marketing tools.

Credit Suisse’s data on 11 fashion retailers found that fast fashion providers such as Forever21 and H&M had the largest Instagram following at more than six million each. This group also demonstrated the highest levels of engagement, measured as the percentage of followers that like each post.

Privately owned U.K.-based retailer Primark Stores Ltd. led the way in this measure at 2.6 per cent, followed by Forever21 at 2.4 per cent.

In the department store segment, Nordstrom is far ahead of the competition with about 800,000 followers and an average of 15,000 likes per photo. After that, retailers’ Instagram tallies come in from most to least fashionable, with Neiman Marcus, Saks, Macy’s, Kohl’s and JCPenney ranking in that order.

Meanwhile, Exstein found that off-price retailers TJ Maxx and Nordstrom Rack fell near the middle of the department store range in terms of followers and engagement.

The challenge, of course, is for retailers to best allocate their time and money amid a growing number of social media choices in the market.

“While this will foster more one-on-one conversations between retailers and consumers, it also challenges the retailer to deal with a shifting marketplace and the declining (but still effective) impact of mass media channels,” Exstein said.